Do we have the same legal system as Denmark?
Obviously not, but as in all monarchies, royal titles and styles are in the gift of the Sovereign.
He/she can bestow or remove them at the stroke of a pen.
If King, Queen, Prince, Princess is not a bloodline then we can elect/place/put whomever into the role.
Think it through.
I don't need to 'think it through', thanks.
If you read my post, you'll have seen that I don't consider it at all likely that Harry's title will be removed. It's theoretically possible but extremely improbable.
However, I was responding to the poster who said 'once a Prince, always a Prince'. That is not actually true. Royal titles are a privilege granted by the Monarch, who can revoke them at any time and for any reason.